Channel capacity optimization for packet services

ABSTRACT

A radio network controller (RNC) application controls packet communications through base stations serving wireless remote stations. In the embodiments, the RNC stores each packet received for a wireless remote station in a buffer and maintains a BCN counter value representing the amount of buffered data. The RNC maintains a maximum accumulation timer (Timer acc ), and it restarts an inter-packet arrival timer (Timer int ) upon receipt of each packet for the station. The RNC initiates transmissions to the station in response to certain events, including expiration of either of the timers Timer int  and Timer acc , and if the BCN counter value exceeds a threshold. However, the transmissions use either a dedicated channel cell-state or a forward access channel state, depending on which event triggered each transmission. The RNC also may instruct the remote station to return to the forward access channel state following communication in the dedicated channel cell-state.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/290,642 entitled “CHANNEL CAPACITY OPTIMIZATION FOR PACKET SERVICES ”filed on May 15, 2001, the disclosure of which is entirely incorporatedherein by reference.

FIELD OF ENDEAVOR

The present subject matter relates to spread-spectrum communications,and more particularly to a code-division-multiple-access (CDMA)cellular, packet-switched communication system, which comprises a radionetwork controller (RNC), a plurality of base stations and a pluralityof remote stations. The subject matter relates more particularly tomethods to facilitate transitions between different channels andperformance of the channels, in such a system.

BACKGROUND

Recent developments in wireless communications technologies have allowedexpansion of service offerings from the original voice telephone servicemodel to include a number of services supporting packet datacommunications. As customers become increasingly familiar with dataservices offered through landline networks, they are increasinglydemanding comparable Quality of Service (QoS) data communications in thewireless domain, for example to maintain service while mobilesubscribers roam freely or to provide remote service in locations wherewireless loops are preferable to landline subscriber loops. A number oftechnologies support packet data communications in the wireless domain.

Under the currently proposed W-CDMA technical specification, there isonly one type of dedicated transport channel, the Dedicated Channel(DCH), which can be either a downlink or an uplink transport channel.There are six types of common transport channels:

1. The Broadcast Channel (BCH)—downlink;

2. The Forward Access Channel (FACH)—downlink;

3. The Paging Channel (PCH)—downlink;

4. The Random Access Channel (RACH)—uplink;

5. The Common Packet Channel (CPCH)—uplink; and

6. The Downlink Shared Channel (DSCH)—shared downlink, associated withone or several downlink DCH.

With these transport channels, there are two states in the connectedmode that can potentially be used to transfer packet data over theW-CDMA air interface: the Cell-FACH state and the Cell-DCH state.

In the Cell-FACH state, there are two sub-states: the RACH/FACHsub-state and the CPCH/FACH sub-state. A mobile station in the CPCH/FACHsub-state is prepared to send packets via the CPCH while tuned in to theFACH for downlink messages. In the Cell-FACH state, the Radio NetworkController (RNC) can allocate RACH or CPCH resources for uplinktransmission. CPCH and RACH may be assigned by the RNC as defaultchannels in the uplink without using uplink resources until they areneeded for transmission of uplink data. RACH is able to transmit verysmall Packet Data Units (PDUs) effectively. RACH capacity is limited to9 bytes at cell edge or to 75 bytes when the mobile station is close tothe base station. Sequential RACH transmissions may be used to transportmore PDUs than a single RACH may carry, however, the RACH accessprocedure must be executed for each RACH access and the subsequent delayis significant. The RNC sets a threshold measurement of traffic volumein the mobile station, essentially instructing the mobile station tosend a measurement report to the RNC when, for example, the trafficvolume in the mobile station uplink buffer exceeds the capacity of twoRACH transmissions. That would be the load at which it would make senseto utilize a higher capacity channel to transmit the buffered uplinkdata. If the measurement report is triggered, the RNC may assign CPCHresources to empty the uplink buffer or can switch the mobile station toCell-DCH state.

CPCH may be assigned instead of RACH, to provide higher capacity uplinktransport. A single CPCH access may transport up to 576×16 bytes of dataat the cell edge (64 frames at SF 16) or up to 36,864 bytes when themobile station is near the base station (64 frames at Spreading Factor4). When CPCH resources are assigned to a mobile station, the RNC sets athreshold measurement of traffic volume in the mobile station,essentially instructing the mobile station to send a measurement reportto the RNC when traffic volume in the mobile station uplink bufferexceeds the capacity of five to ten CPCH transmissions. Consecutive RACHor CPCH accesses may be used until the uplink buffers are emptied.

In the Cell-DCH state, there are the DCH/DCH sub-state and theDCH/DCH+DSCH sub-state. That means the mobile station sends packet datavia the DCH uplink and is tuned to receive data downlink via either theDCH or the DCH+DSCH. The DSCH is a code-sharing mechanism in thedownlink direction and is more desirable when data traffic is bursty.The DCH is more suitable for streaming traffic and is not a resourceefficient means of transmitting bursty uplink data. In the uplink, DCHis different in that dedicated resources in the uplink must be allocatedby the RNC without complete knowledge about the amount of data to betransmitted in the uplink. For this reason an inactivity timer is usedin DCH to determine if the uplink buffer at a mobile station is emptied.The RNC will measure the time period in the uplink during which there isno uplink data transmission. When this period exceeds the inactivitytimer setting, the RNC will reconfigure the mobile station to Cell-FACH.In the downlink, the Radio Network Controller (RNC) can allocate eitherDCH or DCH+DSCH resources for packet data transmission. Similarly, theRNC does not have complete knowledge of future packet arrivals and usesinstead inactivity timers to measure the time period in the downlinkduring which there is no data transmission. When this period exceeds theinactivity timer setting, the RNC will reconfigure the mobile station toCell-FACH. These inactivity timers in CELL-DCH lead to substantialoverhead and inefficiencies when the data traffic is bursty, thusreducing capacity.

For certain types of packet data applications (e.g. interactiveservice), ideally, one would like to use a Cell-FACH (e.g. CPCH/FACHsub-state) for uplink traffic and switch to a Cell-DCH state (e.g.DCH/DCH+DSCH sub-state) for downlink traffic. The reason is that thereare certain deficiencies with both states. In Cell-FACH state, FACHdownlink does not have closed loop power control and has only limitedcapability to handle large packets, whereas in the Cell-DCH state, as inany circuit-switched packet channel, there is a lot of wastage oflimited resources. However, a problem with the proposed frequentswitching is that a mobile station while residing in the Cell-DCH statecannot be de-allocated immediately after transmission of packet data dueto the inactivity timer.

Also, when a group of packets arrive from afar, as in the case of abackbone network, there will often be time-gaps between these packets.When the RNC assigns channel resources immediately after the arrival ofthe first packet and does not release such resources until the lastpacket of the train arrives, the channel hold-up time will increase,thus creating inefficiencies.

SUMMARY

The inventions disclosed here deal with this type of deficiencies in theCell-DCH state and the transition criteria or improvement between theCell-FACH and Cell-DCH states on CDMA networks. The concepts andimprovements described herein can also be generalized and applied toother channels as well as to other wireless digital packet communicationnetworks.

The inventive concepts include a method for grouping a plurality ofpackets and sending these grouped packets in a shorter connecting time.This methodology introduces a quick release, for example, of the DCHresource associated with DCH or DCH+DSCH. By grouping the plurality ofpackets or reducing the release time of the DCH, the mobile station willmore easily oscillate between the Cell-FACH and Cell-DCH states tosupport interactive type or the near-real time conversationalapplications of packet communications.

A general objective of the invention is to remove the inefficienciesassociated with bursty data.

A further objective is to efficiently configure limited physical channelresources to various mobile stations. By reducing the connection time ofa channel, the mobile station also reduces power consumption.

Another objective relates to provide a mechanism to release the DCHresources associated with the Cell-DCH state quickly.

A further objective is to enable mobile stations to oscillate betweenthe Cell-FACH and Cell-DCH states.

A wireless packet communication network, such as acode-division-multiple-access (CDMA) telecommunication system employingspread-spectrum modulation, has a radio network controller (RNC) and aplurality of base stations, which serve a plurality of mobile stations.The term “mobile station” is used here to refer to any wireless remoteuser station, most examples of which are moveable, although some maybeused in fixed wireless applications. In a CDMA embodiment, each basestation has a BS-spread-spectrum transmitter and a BS-spread-spectrumreceiver. Each of the mobile stations has an MS-spread-spectrumtransmitter and an MS-spread-spectrum receiver.

The RNC may be a physical network control node or a control applicationrunning on a network node that also implements other functions, forexample on each of the base stations. In the preferred embodiment, theRNC monitors channel configuration, based on traffic measurementinformation of communications through the base stations for the mobilestations. Based on the traffic demand or a projection thereof, the RNCconfigures the physical channel resources within each cell.

The Radio Network Controller (RNC) waits to receive a packet for amobile station (MS) from a core network. In accord with one inventivetechnique, while waiting for the first packet, the RNC sets its maximumpacket accumulation timer, Timer_(acc), to a predetermined time andresets the buffer content number, of the BCN buffer. The T_(acc) ispreferably less than the time that causes the communication orapplication to time-out (e.g. TCP/IP time-out).

Upon receiving the packet, the RNC keeps the packet in its buffer andresets its maximum inter-packet arrival timer, Timer_(int), and updatesthe BCN counter value. The RNC then compares the updated BCN countervalue with a predetermined BCNX, the buffer size threshold for switchingto Cell-DCH state. If the BCN counter value is less than BCNX, the RNCwill wait for a next packet for the same recipient MS until Timer_(int)expires. If the RNC receives a next packet for the recipient MS beforeTimer_(int) expires, upon receiving the next packet, it again keeps thisnext packet, along with any previously accumulated ones, in its buffer,resets Timer_(int), updates the BCN counter value and compares BCNcounter value with BCNX. The RNC repeats this process until any one ofthree conditions is met: (1) No further packet for the same recipient MSarrives before Timer_(int) expires; (2) Timer_(acc) expires; or (3) BCNcounter value is greater than BCNX. In the case of (1) or (2), since theCell-DCH switch criteria has not been triggered, the RNC will schedulethe BS to send all accumulated packet(s) in its buffer to the recipientMS via FACH (Cell-FACH). In the case of (3), the Cell-DCH switchcriteria is triggered, the RNC will send out a Physical ChannelReconfiguration message to instruct the recipient MS to switch toCell-DCH and schedule the BS to send all accumulated packets in itsbuffer to the recipient MS via DCH or DSCH (Cell-DCH). Upon schedulingthe delivery of any packets in the buffer from the BS to the MS, the RNCresets its BCN counter value to zero.

Upon delivery of the packets, the RCN will need to determine whether theMS should stay in its current state or switch to another state. Thedetailed description teaches a method for such determination, althoughthe determination to switch states may be based on other conventionalmethods common in the art.

The RNC can detect if another packet has arrived for the recipient MSwithin T_(inact) ms. T_(inact) can be set to zero or any other valuesdeemed appropriate. T_(inact) can also be a variable set to coincidewith the end of the scheduled transmission of the accumulated packets.If there is not another packet for recipient MS within T_(inact) ms, theRNC will schedule a Physical Channel Reconfiguration message to instructthe recipient MS to release the DSCH and switch back to Cell-FACH state.Likewise, the buffer size also provides a way to measure congestion inthe current channel. When the packet arrival rate exceeds the rate atwhich RNC can send out packets, packet accumulation will result in alarge buffer. The RNC monitors the buffer content/size and when thebuffer size exceeds a pre-determined threshold, the RNC will configurethe BS to send the accumulated and scheduled packets via DCH.

Aspects of invention include methodologies for implementing suchallocation of channel resources for packet transmissions based ontraffic conditions, using the techniques outlined above. Other aspectsof invention relate to networks and/or network controllers or othercomponents for implementing those techniques.

Additional objects, advantages and novel features of the embodimentswill be set forth in part in the description which follows, and in partwill become apparent to those skilled in the art upon examination of thefollowing and the accompanying drawings or may be learned by productionor operation of the embodiments. The objects and advantages of theinventive concepts may be realized and attained by means of themethodologies, instrumentalities and combinations particularly pointedout in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict preferred embodiments by way of example, notby way of limitations. In the figures, like reference numerals refer tothe same or similar elements.

FIG. 1 is a functional block diagram of a simplified CDMA TerrestrialRadio Access network architecture, capable of implementing thecommunications in accord with the present invention.

FIG. 2 is a functional block diagram of a CDMA network, capable ofimplementing the communications in accord with the present invention.

FIG. 3 is a functional block diagram of a spread spectrum base stationfor use in a network of the type shown in FIG. 2.

FIG. 4 is a functional block diagram of a spread spectrum remote ormobile station for use in a network of the type shown in FIG. 2.

FIG. 5 is a process flow diagram illustrating an example of the RNCscheduling procedure.

FIG. 6 is a more detailed process flow diagram of FIG. 5 illustrating anexample of the RNC scheduling procedure using buffer size as the switchcriteria.

FIG. 7 is a more detailed process flow diagram of FIG. 5 illustrating anexample of the RNC scheduling procedure using accumulation timer as theswitch criteria.

FIG. 8 is a timing diagram showing several examples of receipt andtransmission of groups of packets for a particular mobile station, andthe relationship thereof to certain timers used in one embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The subject matter disclosed involves a packet mode DCH/DCH+DSCHmethodology for releasing the DCH resources associated with Cell-DCHstate in a spread spectrum wireless communication network. The inventiveaccess methodology accommodates bursty traffic in an optimum manner.Reference now is made in detail to the presently preferred embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals indicate like elements throughout the severalviews.

In a preferred embodiment (FIGS. 1 and 2), the CDMA system comprises aradio network controller (RNC) 11, a plurality of base stations 13 and aplurality of mobile stations 15. FIG. 1 shows a simplified CDMATerrestrial Radio Access network architecture As such, FIG. 1 provides arelatively higher level illustration, with a core network 9 providingtwo-way packet data communications to and from a plurality of radionetwork subsystems (RNSs) 10. The RNCs 11 in the radio networksubsystems 10 may be interconnected, for example by the line 12.

With reference to the more detailed version shown in FIG. 2, each basestation (BS) 13 has BS-spread-spectrum transmitter and aBS-spread-spectrum receiver, shown as a single transceiver (XSCV′R)system 17 for simplicity in this drawing. Each of the mobile stations(MS) 15 has an MS-spread-spectrum transmitter and an MS-spread-spectrumreceiver (not separately shown). Exemplary transmitters and receiversfor use in the BS and MS network elements are discussed in more detailbelow with regard to FIGS. 3 and 4. In a typical embodiment, the radionetwork controller (RNC) 11 provides two-way packet data communicationsto a wide area network, shown by way of example as a packet-switchednetwork 19. The RNC 11 and the network 19 provide the MS units 15 withtwo-way packet data communications services to enable communication toand from devices, represented by way of example by the IP telephone 21,the personal computer (PC) 23 and the server 25.

The CDMA system provides a number of logically different channels forupstream and downstream communications over the air-link interface. Eachchannel is defined by one or more of the codes, for example thespreading code and/or the scrambling code. Several of the channels arecommon channels, but most of the channels are used for uplink ordownlink packet communications between the base stations 13 and themobile stations 15.

The RNC 11 measures traffic through the base stations 13 going to andfrom the mobile stations 15. In this way, the radio network controller(RNC) 11 monitors traffic demand in the illustrated network. The RNC 11assigns physical channel resources to the mobile stations 15, byre-configuring the state of packet data connected mode of each mobilestation 15 within each cell of each base station 13. Each mobile station15 in packet data connected mode is either in Cell-FACH state or inCell-DCH state.

As noted earlier, the Cell-DCH state includes two sub-states the DCH/DCHsub-state and the DCH/DCH+DSCH sub-state. In each sub-state, the mobilestation (MS) 15 sends packet data via the Dedicated CHannel (DCH)uplink. The mobile station (MS) 15 tunes to receive downlink data, viaeither the DCH or the DCH+DSCH. In the downlink, the Radio NetworkController (RNC) 11 allocates either DCH or DCH+DSCH resources forpacket data transmission. The Downlink Shared CHannel (DSCH) is aPhysical Channel that provides a code-sharing mechanism in the downlinkdirection and is desirable when data traffic is bursty.

The Cell-FACH state also has two sub-states: the RACH/FACH sub-state andthe CPCH/FACH sub-state. A mobile station in the CPCH/FACH sub-state isprepared to send packets via the CPCH while tuned in to the FACH fordownlink messages. In the Cell-FACH state, the Radio Network Controller(RNC) 11 can allocate RACH or CPCH resources for uplink transmission.

In accord with the present access methodology, when the RNC 11 firstreceives packets for a mobile station (MS) from the core or from thepacket network, the RNC allocates resources for their transmission. TheRNC 11 buffers the first packet and resets two timers. One timerTimer_(int) specifies the maximum inter-packet arrival time T_(int),that is to say, the maximum time that the RNC 11 will wait betweenpackets intended for one station 15 without transmitting. The othertimer Timer_(acc) specifies the maximum packet accumulation timeT_(acc), that is to say, the maximum time over which the RNC 11 willaccumulate packets intended for one station 15 without transmitting. TheRNC 11 also updates its buffer size denotes by the BCN counter value.

The BCN counter value is compared to BCNX, a predetermined threshold forswitching to Cell-DCH state. If the BCN counter value exceeds BCNX, thenthe RNC 11 can proceed to immediate transmission of the accumulatedpackets to the recipient mobile station MS 15 by first switching the MS15 to the Cell-DCH state.

The maximum packet accumulation timer Timer_(acc) defines the time limitT_(acc) within which the network side components, e.g. the RNC and thebase station, must transmit the oldest of the accumulated data. TheT_(acc) is preferably less than the time that causes the communicationor application to time-out (e.g. TCP/IP time-out). At the end of thistime, the RNC 11 will initiate transmission of whatever packet orpackets it has received from the core network 9 or the packet network 19since the receipt of the first (oldest) packet in the buffer (andactivation of the timers). The RNC 11 initiates transmission of thebuffered packets for the particular station 15, on a first-in-first-outbasis. The expiration of Timer_(acc) causes the system to transmit usingthe Cell-FACH state.

The maximum inter-packet arrival time T_(int), specified by the timerTimer_(int), defines a time limit to wait for new packets to arrive fromthe core network 9 or the packet network 19, intended for the particularmobile station 15. If no packets arrive, within this time interval, thenthe RNC 11 shall proceed to the immediate transmission of the bufferedpacket data to the recipient mobile station MS 15.

When no additional packets arrive for the same recipient MS within aT_(int) interval, the RNC 11 immediately sends all accumulated packet(s)in its buffer through base station (BS) 13 to the recipient MS 15 viaFACH (Cell-FACH). However, if the RNC 11 receives a new packet, for therecipient MS, before timer Timer_(int) expires, the RNC 11 adds that newpacket to those previously accumulated in its buffer, resetsTimer_(int), updates the value for the BCN counter, and waits again forthe next packet. The RNC repeats this process until the limit T_(acc)for Timer_(acc) expires. When Timer_(acc) expires, the RNC 11 schedulesthe base station (BS) 13 to send all accumulated packets in its bufferto the recipient MS 14 via FACH.

If at anytime the updated BCN counter value exceeds BCNX, the RNC 11sends a Physical Channel Reconfiguration message to instruct therecipient MS to switch back to Cell-DCH and then sends all accumulatedpackets in its buffer, to the recipient MS 14 via DCH or DSCH(Cell-DCH).

If the RNC 11 has scheduled transmission in the Cell-DCH state, the RNCpreferably detects if there is another packet arriving for recipient MSwithin a period of T_(inact) ms, that is to say within a maximuminactivity interval. If there is no further packet for the recipient MS15 within T_(inact) time, the RNC 11 schedules a Physical ChannelReconfiguration message to instruct the recipient MS to release the DSCHand switch back to Cell-FACH.

FIG. 3 illustrates a presently preferred embodiment of a BSspread-spectrum transmitter and a BS spread-spectrum receiver,essentially in the form of a base-band processor for performing the PHYlayer functions. The BS spread-spectrum transmitter and the BSspread-spectrum receiver form one of the transceivers 17 at a basestation 13. The BS spread-spectrum receiver includes an antenna 309coupled to a circulator 310, a receiver radio frequency (RF) section311, a local oscillator 313, a quadrature demodulator 312, and ananalog-to-digital converter 314. The receiver RF section 311 is coupledbetween the circulator 310 and the quadrature demodulator 312. Thequadrature demodulator is coupled to the local oscillator 313 and to theanalog to digital converter 314. The output of the analog-to-digitalconverter 315 is coupled to a programmable-matched filter 315.

A preamble processor 316, pilot processor 317 and data-and-controlprocessor 318 are coupled to the programmable-matched filter 315. Acontroller 319 is coupled to the preamble processor 316, pilot processor317 and data-and-control processor 318. A de-interleaver 320 is coupledbetween the controller 319 and a forward-error-correction (FEC) decoder321. The decoder 321 outputs data and signaling received via the ULchannel to the MAC layer (not shown).

The BS spread-spectrum transmitter includes a forward-error-correction(FEC) encoder 322 coupled to an interleaver 323. A packet formatter 324is coupled to the interleaver 323 and to the controller 319. A variablegain device 325 is coupled between the packet formatter 324 and aproduct device 326. A spreading-sequence generator 327 is coupled to theproduct device 326. A digital-to-analog converter 328 is coupled betweenthe product device 328 and quadrature modulator 329. The quadraturemodulator 329 is coupled to the local oscillator 313 and a transmitterRF section 330. The transmitter RF section 330 is coupled to thecirculator 310.

The controller 319 has control links coupled to the analog-to-digitalconverter 314, the programmable-matched filter 315, the preambleprocessor 316, the digital-to-analog converter 328, the spreadingsequence generator 327, the variable gain device 325, the packetformatter 324, the de-interleaver 320, the FEC decoder 321, theinterleaver 323 and the FEC encoder 322.

A received spread-spectrum signal from antenna 309 passes throughcirculator 310 and is amplified and filtered by the receiver RF section311. The local oscillator 313 generates a local signal, which thequadrature demodulator 312 uses to demodulate in-phase and quadraturephase components of the received spread-spectrum signal. Theanalog-to-digital converter 314 converts the in-phase component and thequadrature-phase component to digital signals. These functions are wellknown in the art, and variations to this block diagram can accomplishthe same functions.

The programmable-matched filter 315 despreads the receivedspread-spectrum signal components. A correlator, as an alternative, maybe used as an equivalent means for despeading the receivedspread-spectrum signal.

The preamble processor 316 detects a preamble portion of the receivedspread-spectrum signal. The pilot processor 317 detects and synchronizesto a pilot portion of the received spread-spectrum signal. The data andcontrol processor 318 detects and processes the data portion of thereceived spread-spectrum signal. Detected data passes through thecontroller 319 to the de-interleaver 320 and FEC decoder 321. Data andsignaling from the up-link are outputted from the FEC decoder 321 to thehigher layer elements in or associated with the BS 13 and through thelink to the RNC 11.

The RNC 11 supplies data and signaling over a link to the base station.In the BS transceiver, the MAC layer elements supply data and signalinginformation, intended for down-link transmission, to the input of theFEC encoder 322. The signaling and data are FEC encoded by the FECencoder 322, and interleaved by the interleaver 323. The packetformatter 324 formats data, signaling, acknowledgment signal, collisiondetection signal, pilot signal and transmitting power control (TPC)signal into appropriate packets. Each packet is outputted from thepacket formatter 324, and the packet level is amplified or attenuated bythe variable gain device 325. The packet is spread-spectrum processed bythe product device 326, with a spreading chip-sequence from thespreading-sequence generator 327. The packet is converted to an analogsignal by the digital-to-analog converter 328, and in-phase andquadrature-phase components are generated by the quadrature modulator329 using a signal from local oscillator 313. The modulated down-linkpacket is translated to a carrier frequency, filtered and amplified bythe transmitter RF section 330, and then it passes through thecirculator 310 and is radiated by antenna 309.

FIG. 4 shows an embodiment of an MS spread-spectrum transmitter and anMS spread-spectrum receiver, essentially in the form of a base-bandprocessor for performing the PHY layer transceiver functions. The MSspread-spectrum transmitter and the MS spread-spectrum receiver arelocated at the remote or mobile station (MS) 15. The MS spread-spectrumreceiver includes an antenna 409 coupled to a circulator 410, a receiverradio frequency (RF) section 411, a local oscillator 413, a quadraturedemodulator 412, and an analog-to-digital converter 414. The receiver RFsection 411 is coupled between the circulator 410 and the quadraturedemodulator 412. The quadrature demodulator is coupled to the localoscillator 413 and to the analog to digital converter 414. The output ofthe analog-to-digital converter 415 is coupled to a programmable-matchedfilter 415.

An acknowledgment detector 416, pilot processor 417 and data-and-controlprocessor 418 are coupled to the programmable-matched filter 415. Acontroller 419 is coupled to the acknowledgment detector 416, pilotprocessor 417 and data-and-control processor 418. A de-interleaver 420is coupled between the controller 419 and a forward-error-correction(FEC) decoder 421. The decoder 421 outputs data and signaling receivedvia the DL channel to the MAC layer elements (not shown) of the MS.

The MS spread-spectrum transmitter includes a forward-error-correction(FEC) encoder 422 coupled to an interleaver 423. A packet formatter 424is coupled through a multiplexer 451 to the interleaver 423. The packetformatter 424 also is coupled to the controller 419. A preamblegenerator 452 and a pilot generator 453 are coupled to the multiplexer451. A variable gain device 425 is coupled between the packet formatter424 and a product device 426. A spreading-sequence generator 427 iscoupled to the product device 426. A digital-to-analog converter 428 iscoupled between the product device 428 and quadrature modulator 429. Thequadrature modulator 429 is coupled to the local oscillator 413 and atransmitter RF section 430. The transmitter RF section 430 is coupled tothe circulator 410.

The controller 419 has control links coupled to the analog-to-digitalconverter 414, the programmable-matched filter 415, the acknowledgmentdetector 416, the digital-to-analog converter 428, the spreadingsequence generator 427, the variable gain device 425, the packetformatter 424, the de-interleaver 420, the FEC decoder 421, theinterleaver 423, the FEC encoder 422, the preamble generator 452 and thepilot generator 453.

A received spread-spectrum signal from antenna 409 passes throughcirculator 410 and is amplified and filtered by the receiver RF section411. The local oscillator 413 generates a local signal, which thequadrature demodulator 412 uses to demodulate in-phase and quadraturephase components of the received spread-spectrum signal. Theanalog-to-digital converter 414 converts the in-phase component and thequadrature-phase component to digital signals. These functions are wellknown in the art, and variations to this block diagram can accomplishthe same functions.

The programmable-matched filter 415 despreads the receivedspread-spectrum signal components. A correlator, as an alternative, maybe used as an equivalent means for despeading the receivedspread-spectrum signal.

The acknowledgment detector 416 detects certain acknowledgments in thereceived spread-spectrum signal. The pilot processor 417 detects andsynchronizes to a pilot portion of the received spread-spectrum signal.The data and control processor 418 detects and processes the dataportion of the received spread-spectrum signal. Detected data passesthrough the controller 419 to the de-interleaver 420 and FEC decoder421. Data and signaling from the DL are outputted from the FEC decoder421 to the higher level elements in or associated with the MS 15.

In the MS transceiver, the MAC layer elements supply data and signalinginformation intended for transmission over the up-link channel, to theinput of the FEC encoder 422. Data and signaling information are FECencoded by FEC encoder 422, and interleaved by interleaver 423. Thepreamble generator 452 generates a preamble, and the pilot generator 453generates a pilot for the preamble. The multiplexer 451 multiplexes thedata, preamble and pilot, and the packet formatter 424 formats thepreamble, pilot and data into a common-packet channel packet. Further,the packet formatter 424 formats data, signaling, acknowledgment signal,collision detection signal, pilot signal and TPC signal into a packet.The packet formatter 424 outputs the packet, and the packet level isamplified or attenuated by variable gain device 425. The packet isspread-spectrum processed by product device 426, with a spreadingchip-sequence from spreading-sequence generator 427. The packet isconverted to an analog signal by digital-to-analog converter 428, andquadrature modulator 429 using a signal from local oscillator 413generates in-phase and quadrature-phase components. The modulatedup-link packet is translated to a carrier frequency, filtered andamplified by the transmitter RF section 430 and then it passes throughthe circulator 430 and is radiated by the antenna 409.

U.S. Pat. No. 6,169,759 to Kanterakis et al. issued Jan. 2, 2001provides a more detailed description of the operation of the PHYtransceivers shown in FIGS. 3 and 4, for example in a CPCH type channeltransmission.

FIG. 5 is a flow-chart illustrating the inventive processing, from theperspective of the RNC and/or one of the associated base stations.

FIG. 8 is an illustration of several examples of incoming and outgoingpackets of the RNC 11, in relation to the various timers and showsseveral examples, which are useful in explaining the inventiveoperations. The top line of pulses (a) represents incoming packets, forexample as received at the RNC 11. The timing intervals T appear abovethat line. The middle line (b) represents packet transmissions from thebase station (BS) 13 to a specific mobile station (MS) 15 via FACH. Thebottom line (c) represents packet transmissions from the base station(BS) 13 to a specific mobile station (MS) 15 via DSCH.

Assume for example, that the RNC 11 received the first four packets, asshown to the left on line (a) of FIG. 8. Upon receipt of the firstpacket (S51 in FIG. 5), the RNC 11 resets and starts operation of themaximum inter-packet arrival timer, Timer_(int), and the maximum packetaccumulation timer, Timer_(acc) (step S52). The RNC 11 also sets thevalue of the BCN counter for the amount of data in its packet buffer.

The timers may be implemented in any convenient manner. For example, anyof the timers used herein can use a downcount approach, that is to sayreset to maximum and downcount to zero. Any of the timers mayalternatively implement an up-count approach, where the timer is resetto 0 and counts up to a maximum or threshold value. The timers could beanalog, but preferably are implemented as digital logic, as part of theRNC application program.

In the process flow of FIG. 5, the RNC 11 checks the status ofTimer_(acc) in step S53. If the check of Timer_(acc) indicates that themaximum packet accumulation time T_(acc) has not passed since thearrival of the first packet, then the RNC 11 checks to determine if anew packet has been received before expiration of Timer_(int) (stepS54). If a new packet has arrived within the T_(int) interval, theprocess branches from S54 to S55. The RNC 11 places the packet in itsbuffer. The maximum inter-packet arrival timer Timer_(int) is reset eachtime one of the packets for the mobile station MS arrives before thattimer expires (S55). Also, the RNC increments the BCN counter value toreflect buffering of the data of the new packet. After each reset of theinter-packet arrival timer Timer_(int), the RNC checks the amount of thebuffered data (S56) and if the BCN counter does not exceed the thresholdBCNX, the RNC processing loops back to step S53.

In this first illustrated example (first part of FIG. 8), the RNC 11receives only the four packets, and at some point after receipt of thefourth packet, the maximum packet accumulation timer Timer_(acc) runsout. When Timer_(acc) expires, the process flow branches at step S53 tothe state switch decision in step S57 (FIG. 5). In the example (FIG. 8),the RNC 11 causes the base station BS 11 to send all accumulated packetsin its buffer to the recipient MS_(n) via FACH. Hence, in line (b) ofFIG. 8, the BS begins sending the four packets sequentially, startingsubstantially at the time when Timer_(acc) expired.

The RNC will use the Cell-DCH state only when the BCN counter valueexceeds BCNX and when it has received packets and the MS_(n) is still inthe Cell-DCH state. In this case, assuming the MS_(n) was in theCell-FACH state, the first four pulses received by the RNC (FIG. 8,first part line (a) and of line (b)), will be sent by FACH (S60), andthere is no need for a PHY RECONFIG message. As a result, the basestation sends the four accumulated packets in a group and the mobilestation 15 receives the packets as a FACH communication.

In the next example shown in FIG. 8, the RNC subsequently receives aseries of ten packets intended for the mobile station (MS) 15, withsomewhat random spacing therebetween (next ten packets on line (a)). Inthis example, the size of the buffered packet data reaches the switchthreshold, BCNX, after receipt of the sixth packet but before themaximum packet accumulation timer Timer_(acc) runs out. Hence, theprocess flow in FIG. 5 reaches the state switch decision S57 from theBCN counter value threshold decision S56. In response, the RNC 11 causesthe base station BS 11 to send a Physical Channel ReconfigurationMessage (S58) to the MS_(n) 15 and then send all accumulated packets inits buffer to the recipient MS_(n) via DSCH (S59), at this point thelatest six buffered packets, as shown in line (c) of FIG. 8. Statedanother way, because the buffered data exceeds the threshold before anytimer expires, and the previous state was for Cell-FACH transmission,the RNC decides to switch to DSCH to provide a ‘Cell-DCH’ communication.

In this embodiment, the RNC 11 also implements an inactivity timerTimer_(inact). If further packets are received before Timer_(inact)expires, the new packets are transmitted while still in the Cell-DCHtransmission. In continuing with this second example, after the firstsix packets in the buffer are transmitted, the inactivity timerTimer_(inact) does not expire before more packets destined for thismobile station 15 arrive. Thus, the RNC will transmit the remaining fourpackets while in the Cell-DCH state.

A decision is made in Step S61 (in FIG. 5), and the RNC 11 instructs thebase station (BS) to transmit a Physical Channel Reconfiguration message(step S62) to the mobile station (MS), as shown by the subsequent shadedpulse in FIG. 8, line (c). Receipt of the Reconfiguration message causesthe intended mobile station (MS) to release the DSCH and switch back toCell FACH state.

In the third illustrated example in FIG. 8, the RNC receives fivepackets for the mobile station. In this case, the timer Timer_(int)expires first. Since MS_(n) is still in the Cell-FACH state, the RNC 11does not send a Physical Channel Reconfiguration message. Essentially,in such a case, the RNC 11 transmits the currently buffered packets viaFACH while MS 15 is in the Cell-FACH state. The remaining twelve packetsin FIG. 8 are transmitted using the Cell-DCH state since the BCN countervalue reaches BCNX before any other timer expires.

FIGS. 6 and 7 show alternate embodiments of somewhat more detailedprocess flows, for the transmission timing and state decision processingby the RNC 11. The Radio Network Controller (RNC) 11 waits to receive apacket for a mobile station (MS) from a core network. While waiting forthe first packet, the RNC sets its maximum packet accumulation timer,Timer_(acc), to a predetermined time and its buffer content number, BCNcounter value, to zero. The value of T_(acc) is preferably less than thetime that causes the communication or application to time-out (e.g.TCP/IP time-out).

Upon receiving a packet, the RNC 11 loads the packet into its buffer andupdates the BCN counter value accordingly.

In the embodiment of FIG. 6, for example, the RNC next compares theupdated BCN counter value with a predetermined BCNX value, the buffersize threshold for switching to Cell-DCH state. If the BCN counter valueis less than BCNX, the RNC will wait for reception of a next packetdestined for the same recipient MS, until either the timer Timer_(int)or the timer Timer_(acc) expires. If the RNC receives a next packet forthe recipient MS before either timer expires, upon receiving the nextpacket, it again keeps this next packet in the buffer, along with anypreviously accumulated ones. At this time, the RNC again resets thetimer Timer_(int), updates the value of the BCN counter for the size ofthe data stored in the buffer and compares the BCN counter value withBCNX.

In the embodiment of FIG. 6, the RNC repeats this process until any oneof three conditions is met: (1) No further packet for the same recipientMS arrives before Timer_(int) expires; (2) Timer_(acc) expires; or (3)BCN counter value is greater than BCNX. When any one of these eventsoccurs, the RNC resets the value of Timer_(acc).

If the buffer size value kept in the BCN counter exceeds BCNX, theCell-DCH switch criteria is triggered, therefore the RNC will send out aPhysical Channel Reconfiguration message (if necessary) to instruct therecipient MS to switch to Cell-DCH. The RNC next schedules the BS tosend all accumulated packets in its buffer to the recipient MS via DCHor DSCH (Cell-DCH). In the embodiment of FIG. 6, when the packets aretransmitted, the RNC checks to see if any further new packet has beenreceived. If so, the RNC returns and schedules transmission of theadditional packet(s) via the existing Cell-DCH state. This transmissionloop repeats unless or until there is no further new packet to send forthe time specified by the inactivity timer Timer_(inact), at which pointa new decision is made as to the state change and processing returns toexpectation of a packet and waiting to receive a new first packet.

In the embodiment of FIG. 6, if the Cell-DCH switch criteria has notbeen triggered, the RNC will schedule the BS to send all accumulatedpacket(s) in its buffer to the recipient MS via FACH (Cell-FACH). Uponscheduling the delivery of any packets in the buffer from the BS to theMS, the RNC resets its BCN counter value to zero. However, if thecurrent cell state is Cell-DCH transmission, the processing enters theloop for checking for a new packet and if found scheduling the BS tosend all accumulated packets in its buffer to the recipient MS via DCHor DSCH (Cell-DCH).

As noted, the initial steps in the embodiment of FIG. 7 are similar tothose in FIG. 6. Upon receiving a packet, the RNC loads the packet inits buffer and updates the BCN counter value. In the embodiment of FIG.7, the RNC resets the arrival timer Timer_(int). The RNC then checks tobe sure that the accumulation timer Timer_(acc) has not expired, and ifnot, the RNC compares the updated BCN counter value with the buffer sizethreshold BCNX for switching to Cell-DCH state. If the BCN counter valueis less than BCNX, the RNC checks the arrival timer Timer_(int) andwhether or not it has received another packet. In this way, the RNC willwait for a next packet for the same recipient MS until Timer_(int)expires.

If the RNC receives a next packet for the recipient MS beforeTimer_(int) expires, upon receiving the next packet, it again storesthis next packet, along with any previously accumulated ones, in itsbuffer, resets the Timer_(int), updates the BCN counter value and checksthe BCN counter value and the timer Timer_(acc). Again, the RNC repeatsthis process until any one of three conditions is met: (1) No furtherpacket for the same recipient MS arrives before Timer_(int) expires; (2)Timer_(acc) expires; or (3) BCN counter value is greater than BCNX.

It is contemplated that some implementations will use Timer_(acc) as thecriteria to switch to Cell-DCH transmission. In such an embodiment, ifafter buffering one or more packets, the accumulation timer Timer_(acc)expires, the RNC will send out a Physical Channel Reconfigurationmessage (if necessary) to instruct the recipient MS to switch toCell-DCH.

However, in the illustrated embodiment, the RNC checks the transmissionstate and the Timer_(acc) state. If not already in the Cell-DCH stateand the Timer_(acc) has not expired, the RNC checks the BCN countervalue. If that value exceeds the threshold BCNX, the RNC next schedulesthe BS to send all accumulated packets in its buffer to the recipient MSvia DCH or DSCH (Cell-DCH). In the embodiment of FIG. 7, if the Cell-DCHswitch criteria has not been triggered, the RNC will schedule the BS tosend all accumulated packet(s) in its buffer to the recipient MS viaFACH (Cell-FACH). Upon scheduling the delivery of any packets in thebuffer from the BS to the MS, the RNC resets its BCN counter value tozero. However, when a new packet arrives, if the current cell state isCell-DCH transmission, the processing jumps to the step for sending allpackets in its buffer to the recipient MS via DCH or DSCH (Cell-DCH).

In either embodiment (FIG. 6 or FIG. 7), in the Cell-DCH state, the RNCcan detect if there is another packet arriving for recipient MS withinT_(inact) ms from the time the last packet was transmitted while in theCell-DCH state. Timer_(inact) is reset to T_(inact) at the time the lastpacket was transmitted while in the Cell-DCH state. If there is notanother packet for recipient MS within T_(inact) ms, the RNC willschedule a Physical Channel Reconfiguration message to instruct therecipient MS to release the DSCH and switch back to Cell-FACH state.Likewise, the buffer size also provides a way to measure congestion inthe current channel. When the packet arrival rate exceeds the rate atwhich the RNC can send out packets, packet accumulation will result in alarge buffer. The RNC monitors the buffer content/size and when thebuffer size exceeds a pre-determined threshold, the RNC will configurethe BS to send the accumulated and scheduled packets via DCH.

In the embodiments, the state control processing was implemented in theradio network controller (RNC) 11. The RNC 11 may be implemented as aseparate packet switching node in the network, which has sufficientprocessing capability that is programmed to detect conditions andprovide instructions to the base stations, in the manner outlined above.Such an RNC node can be implemented with a general purpose programmabledevice having the appropriate packet interfaces for the necessarycommunications and sufficient processing and memory capacity necessaryto perform the necessary routing and control functions. Such a device isthen programmed with the executable code to implement the desired one ofthe processing embodiments, as part of its programming to implement itsother channel allocation and routing functions in the context of theCDMA network.

The term radio network controller or RNC as used herein refers to acontrol functionality or application, for monitoring packet traffic andassigning radio-link resources through control of the base stations. Asshown in the drawings and described above, the exemplary RNC 11 may takethe form of a physically separate node between the core network and anumber of base stations within one radio network system. Those skilledin the art will recognize, however, that the control functionality ofthe RNC may actually reside at any convenient network location orlocations. For example, the RNC functionality may be combined with thatof one or a distributed number of the base stations. Alternatively, theRNC functionality may be implemented in a higher-level network node, forexample within another layer of controller.

While the foregoing has described what are considered to be the bestmode and/or other preferred embodiments, it is understood that variousmodifications may be made therein and that the invention or inventionsdisclosed herein may be implemented in various forms and embodiments,and that they may be applied in numerous applications, only some ofwhich have been described herein. It is intended by the following claimsto claim any and all modifications and variations that fall within thetrue scope of the inventive concepts.

1. In a wireless packet communication network comprising a plurality ofbase stations for serving a wireless remote station, a method of packettransmission to the wireless remote station, comprising the steps of:(a) upon receiving a first packet intended for the wireless remotestation, placing the packet in a buffer and starting an accumulationtimer; (b) starting an inter-packet arrival timer; (c) if an amount ofdata stored in the buffer exceeds a threshold value, sending a messageto the wireless remote station to enter a cell-state for dedicatedchannel communications, and causing a base station to transmit all datafrom the buffer to the wireless remote station over an assigneddown-link channel of the wireless packet communication network in thededicated channel cell-state; (d) if the amount of data stored in thebuffer does not exceed the threshold value, waiting for arrival of afurther packet intended for the wireless remote station; (e) if afurther packet intended for the wireless remote station arrives beforeexpiration of the inter-packet arrival timer, placing the further packetin the buffer, re-starting the inter-packet arrival timer and returningto step (c) to continue further performance of steps of the method; and(f) if the accumulation timer expires while there is data in the buffer,or if no further packet intended for the wireless remote station arrivesbefore expiration of the inter-packet arrival timer, causing the basestation to transmit data from the buffer to the wireless remote stationover a channel for forward access communications. 2-24. (canceled)